1. Field of the Invention
This invention relates to a process for preparing a mixture of polycyclic aromatic polycarboxylic acids that is substantially soluble in acetone but substantially insoluble in water which comprises subjecting a slurry containing coal to reaction with aqueous nitric acid in an atmosphere containing molecular oxygen, mechanically separating the solids in the resulting slurry, extracting the resulting solids with a polar solvent to separate therefrom a mixture of polycyclic aromatic polycarboxylic acids substantially soluble in acetone but substantially insoluble in water and a mixture of polycyclic aromatic polycarboxylic acids substantially insoluble in acetone and substantially insoluble in water.
2. Description of the Prior Art
In our U.S. Pat. No. 4,052,448, which is incorporated herein by reference, we disclosed a process for preparing a mixture of polycyclic aromatic polycarboxylic acids that is substantially soluble in acetone but substantially insoluble in water which involved subjecting a slurry containing coal to reaction with aqueous nitric acid, mechanically separating the solids in the resulting slurry, extracting the resulting solids with a polar solvent and then separating the polar solvent from the extract to recover the mixture of polycyclic aromatic polycarboxylic acids substantially soluble in acetone but substantially insoluble in water.